3 questions; please answer!?

A half pound to one pound difference could be almost anything (clothing, body fluids, etc.) so I do not believe it was your hair. As for your second question, no you can not gain weight from taking vitamins. Vitamins are essential for your body but will not make you gain weight at all. As for a meal plan you should eat a diet that is 30 percent fat, 30 percent protein, and 40 percent carbohydrates. Try to eat around 2000 calories a day.